Multimedia time warping system

ABSTRACT

A multimedia time warping system. The invention allows the user to store selected television broadcast programs while the user is simultaneously watching or reviewing another program. A preferred embodiment of the invention accepts television (TV) input streams in a multitude of forms, for example, National Television Standards Committee (NTSC) or PAL broadcast, and digital forms such as Digital Satellite System (DSS), Digital Broadcast Services (DBS), or Advanced Television Standards Committee (ATSC). The TV streams are converted to an Moving Pictures Experts Group (MPEG) formatted stream for internal transfer and manipulation and are parsed and separated it into video and audio components. The components are stored in temporary buffers. Events are recorded that indicate the type of component that has been found, where it is located, and when it occurred. The program logic is notified that an event has occurred and the data is extracted from the buffers. The parser and event buffer decouple the CPU from having to parse the MPEG stream and from the real time nature of the data streams which allows for slower CPU and bus speeds and translate to lower system costs. The video and audio components are stored on a storage device and when the program is requested for display, the video and audio components are extracted from the storage device and reassembled into an MPEG stream which is sent to a decoder. The decoder converts the MPEG stream into TV output signals and delivers the TV output signals to a TV receiver. User control commands are accepted and sent through the system. These commands affect the flow of said MPEG stream and allow the user to view stored programs with at least the following functions: reverse, fast forward, play, pause, index, fast/slow reverse play, and fast/slow play.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates to the time shifting of television broadcastsignals. More particularly, the invention relates to the real timecapture, storage, and display of television broadcast signals.

2. Description of the Prior Art

The Video Cassette Recorder (VCR) has changed the lives of television(TV) viewers throughout the world. The VCR has offered viewers theflexibility to time-shift TV programs to match their lifestyles.

The viewer stores TV programs onto magnetic tape using the VCR. The VCRgives the viewer the ability to play, rewind, fast forward and pause thestored program material. These functions enable the viewer to pause theprogram playback whenever he desires, fast forward through unwantedprogram material or commercials, and to replay favorite scenes. However,a VCR cannot both capture and play back information at the same time.

One approach to solving this problem is to use several VCRs. Forexample, if two video tape recorders are available, it might be possibleto Ping-Pong between the two. In this case, the first recorder isstarted at the beginning of the program of interest. If the viewerwishes to rewind the broadcast, the second recorder begins recording,while the first recorder is halted, rewound to the appropriate place,and playback initiated. However, at least a third video tape recorder isrequired if the viewer wishes to fast forward to some point in timeafter the initial rewind was requested. In this case, the third recorderstarts recording the broadcast stream while the second is halted andrewound to the appropriate position. Continuing this exercise, one canquickly see that the equipment becomes unwieldy, unreliable, expensive,and hard to operate, while never supporting all desired functions. Inaddition, tapes are of finite length, and may potentially end atinconvenient times, drastically lowering the value of the solution.

The use of digital computer systems to solve this problem has beensuggested. U.S. Pat. No. 5,371,551 issued to Logan et al., on Dec. 6,1994, teaches a method for concurrent video recording and playback. Itpresents a microprocessor controlled broadcast and playback device. Saiddevice compresses and stores video data onto a hard disk. However, thisapproach is difficult to implement because the processor requirementsfor keeping up with the high video rates makes the device expensive andproblematic. The microprocessor must be extremely fast to keep up withthe incoming and outgoing video data.

It would be advantageous to provide a multimedia time warping systemthat gives the user the ability to simultaneously record and play backTV broadcast programs. It would further be advantageous to provide amultimedia time warping system that utilizes an approach that decouplesthe microprocessor from the high video data rates, thereby reducing themicroprocessor and system requirements which are at a premium.

SUMMARY OF THE INVENTION

The invention provides a multimedia time warping system. The inventionutilizes an easily manipulated, low cost multimedia storage and displaysystem that allows the user to view a television broadcast program withthe option of instantly reviewing previous scenes within the program. Inaddition, the invention allows the user to store selected televisionbroadcast programs while the user is simultaneously watching orreviewing another program.

A preferred embodiment of the invention accepts television (TV) inputstreams in a multitude of forms, for example, analog forms such asNational Television Standards Committee (NTSC) or PAL broadcast, anddigital forms such as Digital Satellite System (DSS), Digital BroadcastServices (DBS), or Advanced Television Standards Committee (ATSC).Analog TV streams are converted to an Moving Pictures Experts Group(MPEG) formatted stream for internal transfer and manipulation, whilepre-formatted MPEG streams are extracted from the digital TV signal andpresented in a similar format to encoded analog streams.

The invention parses the resulting MPEG stream and separates it into itsvideo and audio components. It then stores the components into temporarybuffers. Events are recorded that indicate the type of component thathas been found, where it is located, and when it occurred. The programlogic is notified that an event has occurred and the data is extractedfrom the buffers.

The parser and event buffer decouple the CPU from having to parse theMPEG stream and from the real time nature of the data streams. Thisdecoupling allows for slower CPU and bus speeds which translate to lowersystem costs. The video and audio components are stored on a storagedevice. When the program is requested for display, the video and audiocomponents are extracted from the storage device and reassembled into anMPEG stream. The MPEG stream is sent to a decoder. The decoder convertsthe MPEG stream into TV output signals and delivers the TV outputsignals to a TV receiver.

User control commands are accepted and sent through the system. Thesecommands affect the flow of said MPEG stream and allow the user to viewstored programs with at least the following functions: reverse, fastforward, play, pause, index, fast/slow reverse play, and fast/slow play.

Other aspects and advantages of the invention will become apparent fromthe following detailed description in combination with the accompanyingdrawings, illustrating, by way of example, the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block schematic diagram of a high level view of a preferredembodiment of the invention according to the invention;

FIG. 2 is a block schematic diagram of a preferred embodiment of theinvention using multiple input and output modules according to theinvention;

FIG. 3 is a schematic diagram of an Moving Pictures Experts Group (MPEG)data stream and its video and audio components according to theinvention;

FIG. 4 is a block schematic diagram of a parser and four direct memoryaccess (DMA) input engines contained in the Media Switch according tothe invention;

FIG. 5 is a schematic diagram of the components of a packetizedelementary stream (PES) buffer according to the invention;

FIG. 6 is a schematic diagram of the construction of a PES buffer fromthe parsed components in the Media Switch output circular buffers;

FIG. 7 is a block schematic diagram of the Media Switch and the variouscomponents that it communicates with according to the invention;

FIG. 8 is a block schematic diagram of a high level view of the programlogic according to the invention;

FIG. 9 is a block schematic diagram of a class hierarchy of the programlogic according to the invention;

FIG. 10 is a block schematic diagram of a preferred embodiment of theclip cache component of the invention according to the invention;

FIG. 11 is a block schematic diagram of a preferred embodiment of theinvention that emulates a broadcast studio video mixer according to theinvention;

FIG. 12 is a block schematic diagram of a closed caption parseraccording to the invention; and

FIG. 13 is a block schematic diagram of a high level view of a preferredembodiment of the invention utilizing a VCR as an integral component ofthe invention according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention is embodied in a multimedia time warping system. A systemaccording to the invention provides a multimedia storage and displaysystem that allows the user to view a television broadcast program withthe option of instantly reviewing previous scenes within the program.The invention additionally provides the user with the ability to storeselected television broadcast programs while simultaneously watching orreviewing another program and to view stored programs with at least thefollowing functions: reverse, fast forward, play, pause, index,fast/slow reverse play, and fast/slow play.

Referring to FIG. 1, a preferred embodiment of the invention has anInput Section 101, Media Switch 102, and an Output Section 103. TheInput Section 101 takes television (TV) input streams in a multitude offorms, for example, National Television Standards Committee (NTSC) orPAL broadcast, and digital forms such as Digital Satellite System (DSS),Digital Broadcast Services (DBS), or Advanced Television StandardsCommittee (ATSC). DBS, DSS and ATSC are based on standards called MovingPictures Experts Group 2 (MPEG2) and MPEG2 Transport. MPEG2 Transport isa standard for formatting the digital data stream from the TV sourcetransmitter so that a TV receiver can disassemble the input stream tofind programs in the multiplexed signal. The Input Section 101 producesMPEG streams. An MPEG2 transport multiplex supports multiple programs inthe same broadcast channel, with multiple video and audio feeds andprivate data. The Input Section 101 tunes the channel to a particularprogram, extracts a specific MPEG program out of it, and feeds it to therest of the system. Analog TV signals are encoded into a similar MPEGformat using separate video and audio encoders, such that the remainderof the system is unaware of how the signal was obtained. Information maybe modulated into the Vertical Blanking Interval (VBI) of the analog TVsignal in a number of standard ways; for example, the North AmericanBroadcast Teletext Standard (NABTS) may be used to modulate informationonto lines 10 through 20 of an NTSC signal, while the FCC mandates theuse of line 21 for Closed Caption (CC) and Extended Data Services (EDS).Such signals are decoded by the input section and passed to the othersections as if they were delivered via an MPEG2 private data channel.

The Media Switch 102 mediates between a microprocessor CPU 106, harddisk or storage device 105, and memory 104. Input streams are convertedto an MPEG stream and sent to the Media Switch 102. The Media Switch 102buffers the MPEG stream into memory. It then performs two operations ifthe user is watching real time TV: the stream is sent to the OutputSection 103 and it is written simultaneously to the hard disk or storagedevice 105.

The Output Section 103 takes MPEG streams as input and produces ananalog TV signal according to the NTSC, PAL, or other required TVstandards. The Output Section 103 contains an MPEG decoder, On-ScreenDisplay (OSD) generator, analog TV encoder and audio logic. The OSDgenerator allows the program logic to supply images which will beoverlayed on top of the resulting analog TV signal. Additionally, theOutput Section can modulate information supplied by the program logiconto the VBI of the output signal in a number of standard formats,including NABTS, CC and EDS.

With respect to FIG. 2, the invention easily expands to accommodatemultiple Input Sections (tuners) 201, 202, 203, 204, each can be tunedto different types of input. Multiple Output Modules (decoders) 206,207, 208, 209 are added as well. Special effects such as picture in apicture can be implemented with multiple decoders. The Media Switch 205records one program while the user is watching another. This means thata stream can be extracted off the disk while another stream is beingstored onto the disk.

Referring to FIG. 3, the incoming MPEG stream 301 has interleaved video302, 305, 306 and audio 303, 304, 307 segments. These elements must beseparated and recombined to create separate video 308 and audio 309streams or buffers. This is necessary because separate decoders are usedto convert MPEG elements back into audio or video analog components.Such separate delivery requires that time sequence information begenerated so that the decoders may be properly synchronized for accurateplayback of the signal.

The Media Switch enables the program logic to associate proper timesequence information with each segment, possibly embedding it directlyinto the stream. The time sequence information for each segment iscalled a time stamp. These time stamps are monotonically increasing andstart at zero each time the system boots up. This allows the inventionto find any particular spot in any particular video segment. Forexample, if the system needs to read five seconds into an incomingcontiguous video stream that is being cached, the system simply has tostart reading forward into the stream and look for the appropriate timestamp.

A binary search can be performed on a stored file to index into astream. Each stream is stored as a sequence of fixed-size segmentsenabling fast binary searches because of the uniform time stamping. Ifthe user wants to start in the middle of the program, the systemperforms a binary search of the stored segments until it finds theappropriate spot, obtaining the desired results with a minimal amount ofinformation. If the signal were instead stored as an MPEG stream, itwould be necessary to linearly parse the stream from the beginning tofind the desired location.

With respect to FIG. 4, the Media Switch contains four input DirectMemory Access (DMA) engines 402, 403, 404, 405 each DMA engine has anassociated buffer 410, 411, 412, 413. Conceptually, each DMA engine hasa pointer 406, a limit for that pointer 407, a next pointer 408, and alimit for the next pointer 409. Each DMA engine is dedicated to aparticular type of information, for example, video 402, audio 403, andparsed events 405. The buffers 410, 411, 412, 413 are circular andcollect the specific information. The DMA engine increments the pointer406 into the associated buffer until it reaches the limit 407 and thenloads the next pointer 408 and limit 409. Setting the pointer 406 andnext pointer 408 to the same value, along with the corresponding limitvalue creates a circular buffer. The next pointer 408 can be set to adifferent address to provide vector DMA.

The input stream flows through a parser 401. The parser 401 parses thestream looking for MPEG distinguished events indicating the start ofvideo, audio or private data segments. For example, when the parser 401finds a video event, it directs the stream to the video DMA engine 402.The parser 401 buffers up data and DMAs it into the video buffer 410through the video DMA engine 402. At the same time, the parser 401directs an event to the event DMA engine 405 which generates an eventinto the event buffer 413. When the parser 401 sees an audio event, itredirects the byte stream to the audio DMA engine 403 and generates anevent into the event buffer 413. Similarly, when the parser 401 sees aprivate data event, it directs the byte stream to the private data DMAengine 404 and directs an event to the event buffer 413. The MediaSwitch notifies the program logic via an interrupt mechanism when eventsare placed in the event buffer.

Referring to FIGS. 4 and 5, the event buffer 413 is filled by the parser401 with events. Each event 501 in the event buffer has an offset 502,event type 503, and time stamp field 504. The parser 401 provides thetype and offset of each event as it is placed into the buffer. Forexample, when an audio event occurs, the event type field is set to anaudio event and the offset indicates the location in the audio buffer411. The program logic knows where the audio buffer 411 starts and addsthe offset to find the event in the stream. The address offset 502 tellsthe program logic where the next event occurred, but not where it ended.The previous event is cached so the end of the current event can befound as well as the length of the segment.

With respect to FIGS. 5 and 6, the program logic reads accumulatedevents in the event buffer 602 when it is interrupted by the MediaSwitch 601. From these events the program logic generates a sequence oflogical segments 603 which correspond to the parsed MPEG segments 615.The program logic converts the offset 502 into the actual address 610 ofeach segment, and records the event length 609 using the last cachedevent. If the stream was produced by encoding an analog signal, it willnot contain Program Time Stamp (PTS) values, which are used by thedecoders to properly present the resulting output. Thus, the programlogic uses the generated time stamp 504 to calculate a simulated PTS foreach segment and places that into the logical segment time stamp 607. Inthe case of a digital TV stream, PTS values are already encoded in thestream. The program logic extracts this information and places it in thelogical segment time stamp 607.

The program logic continues collecting logical segments 603 until itreaches the fixed buffer size. When this occurs, the program logicgenerates a new buffer, called a Packetized Elementary Stream (PES) 605buffer containing these logical segments 603 in order, plus ancillarycontrol information. Each logical segment points 604 directly to thecircular buffer, e.g., the video buffer 613, filled by the Media Switch601. This new buffer is then passed to other logic components, which mayfurther process the stream in the buffer in some way, such as presentingit for decoding or writing it to the storage media. Thus, the MPEG datais not copied from one location in memory to another by the processor.This results in a more cost effective design since lower memorybandwidth and processor bandwidth is required.

A unique feature of the MPEG stream transformation into PES buffers isthat the data associated with logical segments need not be present inthe buffer itself, as presented above. When a PES buffer is written tostorage, these logical segments are written to the storage medium in thelogical order in which they appear. This has the effect of gatheringcomponents of the stream, whether they be in the video, audio or privatedata circular buffers, into a single linear buffer of stream data on thestorage medium. The buffer is read back from the storage medium with asingle transfer from the storage media, and the logical segmentinformation is updated to correspond with the actual locations in thebuffer 606. Higher level program logic is unaware of thistransformation, since it handles only the logical segments, thus streamdata is easily managed without requiring that the data ever be copiedbetween locations in DRAM by the CPU.

A unique aspect of the Media Switch is the ability to handle high datarates effectively and inexpensively. It performs the functions of takingvideo and audio data in, sending video and audio data out, sending videoand audio data to disk, and extracting video and audio data from thedisk on a low cost platform. Generally, the Media Switch runsasynchronously and autonomously with the microprocessor CPU, using itsDMA capabilities to move large quantities of information with minimalintervention by the CPU.

Referring to FIG. 7, the input side of the Media Switch 701 is connectedto an MPEG encoder 703. There are also circuits specific to MPEG audio704 and vertical blanking interval (VBI) data 702 feeding into the MediaSwitch 701. If a digital TV signal is being processed instead, the MPEGencoder 703 is replaced with an MPEG2 Transport Demultiplexor, and theMPEG audio encoder 704 and VBI decoder 702 are deleted. Thedemultiplexor multiplexes the extracted audio, video and private datachannel streams through the video input Media Switch port.

The parser 705 parses the input data stream from the MPEG encoder 703,audio encoder 704 and VBl decoder 702, or from the transportdemultiplexor in the case of a digital TV stream. The parser 705 detectsthe beginning of all of the important events in a video or audio stream,the start of all of the frames, the start of sequence headers—all of thepieces of information that the program logic needs to know about inorder to both properly play back and perform special effects on thestream, e.g. fast forward, reverse, play, pause, fast/slow play,indexing, and fast/slow reverse play.

The parser 705 places tags 707 into the FIFO 706 when it identifiesvideo or audio segments, or is given private data. The DMA 709 controlswhen these tags are taken out. The tags 707 and the DMA addresses of thesegments are placed into the event queue 708. The frame typeinformation, whether it is a start of a video I-frame, video B-frame,video P-frame, video PES, audio PES, a sequence header, an audio frame,or private data packet, is placed into the event queue 708 along withthe offset in the related circular buffer where the piece of informationwas placed. The program logic operating in the CPU 713 examines eventsin the circular buffer after it is transferred to the DRAM 714.

The Media Switch 701 has a data bus 711 that connects to the CPU 713 andDRAM 714. An address bus 712 is also shared between the Media Switch701, CPU 713, and DRAM 714. A hard disk or storage device 710 isconnected to one of the ports of the Media Switch 701. The Media Switch701 outputs streams to an MPEG video decoder 715 and a separate audiodecoder 717. The audio decoder 717 signals contain audio cues generatedby the system in response to the user's commands on a remote control orother internal events. The decoded audio output from the MPEG decoder isdigitally mixed 718 with the separate audio signal. The resultingsignals contain video, audio, and on-screen displays and are sent to theTV 716.

The Media Switch 701 takes in 8-bit data and sends it to the disk, whileat the same time extracts another stream of data off of the disk andsends it to the MPEG decoder 715. All of the DMA engines described abovecan be working at the same time. The Media Switch 701 can be implementedin hardware using a Field Programmable Gate Array (FPGA), ASIC, ordiscrete logic.

Rather than having to parse through an immense data stream looking forthe start of where each frame would be, the program logic only has tolook at the circular event buffer in DRAM 714 and it can tell where thestart of each frame is and the frame type. This approach saves a largeamount of CPU power, keeping the real time requirements of the CPU 713small. The CPU 713 does not have to be very fast at any point in time.The Media Switch 701 gives the CPU 713 as much time as possible tocomplete tasks. The parsing mechanism 705 and event queue 708 decouplethe CPU 713 from parsing the audio, video, and buffers and the real timenature of the streams, which allows for lower costs. It also allows theuse of a bus structure in a CPU environment that operates at a muchlower clock rate with much cheaper memory than would be requiredotherwise.

The CPU 713 has the ability to queue up one DMA transfer and can set upthe next DMA transfer at its leisure. This gives the CPU 713 large timeintervals within which it can service the DMA controller 709. The CPU713 may respond to a DMA interrupt within a larger time window becauseof the large latency allowed. MPEG streams, whether extracted from anMPEG2 Transport or encoded from an analog TV signal, are typicallyencoded using a technique called Variable Bit Rate encoding (VBR). Thistechnique varies the amount of data required to represent a sequence ofimages by the amount of movement between those images. This techniquecan greatly reduce the required bandwidth for a signal, howeversequences with rapid movement (such as a basketball game) may be encodedwith much greater bandwidth requirements. For example, the HughesDirecTV satellite system encodes signals with anywhere from 1 to 10 Mb/sof required bandwidth, varying from frame to frame. It would bedifficult for any computer system to keep up with such rapidly varyingdata rates without this structure.

With respect to FIG. 8, the program logic within the CPU has threeconceptual components: sources 801, transforms 802, and sinks 803. Thesources 801 produce buffers of data. Transforms 802 process buffers ofdata and sinks 803 consume buffers of data. A transform is responsiblefor allocating and queuing the buffers of data on which it will operate.Buffers are allocated as if “empty” to sources of data, which give themback “full”. The buffers are then queued and given to sinks as “full”,and the sink will return the buffer “empty”.

A source 801 accepts data from encoders, e.g., a digital satellitereceiver. It acquires buffers for this data from the downstreamtransform, packages the data into a buffer, then pushes the buffer downthe pipeline as described above. The source object 801 does not knowanything about the rest of the system. The sink 803 consumes buffers,taking a buffer from the upstream transform, sending the data to thedecoder, and then releasing the buffer for reuse.

There are two types of transforms 802 used: spatial and temporal.Spatial transforms are transforms that perform, for example, an imageconvolution or compression/decompression on the buffered data that ispassing through. Temporal transforms are used when there is no timerelation that is expressible between buffers going in and buffers comingout of a system. Such a transform writes the buffer to a file 804 on thestorage medium. The buffer is pulled out at a later time, sent down thepipeline, and properly sequenced within the stream.

Referring to FIG. 9, a C++ class hierarchy derivation of the programlogic is shown. The TiVo Media Kernel (Tmk) 904, 908, 913 mediates withthe operating system kernel. The kernel provides operations such as:memory allocation, synchronization, and threading. The TmkCore 904, 908,913 structures memory taken from the media kernel as an object. Itprovides operators, new and delete, for constructing and deconstructingthe object. Each object (source 901, transform 902, and sink 903) ismulti-threaded by definition and can run in parallel.

The TmkPipeline class 905, 909, 914 is responsible for flow controlthrough the system. The pipelines point to the next pipeline in the flowfrom source 901 to sink 903. To pause the pipeline, for example, anevent called “pause” is sent to the first object in the pipeline. Theevent is relayed on to the next object and so on down the pipeline. Thisall happens asynchronously to the data going through the pipeline. Thus,similar to applications such as telephony, control of the flow of MPEGstreams is asynchronous and separate from the streams themselves. Thisallows for a simple logic design that is at the same time powerfulenough to support the features described previously, including pause,rewind, fast forward and others. In addition, this structure allows fastand efficient switching between stream sources, since buffered data canbe simply discarded and decoders reset using a single event, after whichdata from the new stream will pass down the pipeline. Such a capabilityis needed, for example, when switching the channel being captured by theinput section, or when switching between a live signal from the inputsection and a stored stream.

The source object 901 is a TmkSource 906 and the transform object 902 isa TmkXfrm 910. These are intermediate classes that define standardbehaviors for the classes in the pipeline. Conceptually, they handshakebuffers down the pipeline. The source object 901 takes data out of aphysical data source, such as the Media Switch, and places it into a PESbuffer. To obtain the buffer, the source object 901 asks the down streamobject in his pipeline for a buffer (allocEmptyBuf). The source object901 is blocked until there is sufficient memory. This means that thepipeline is self-regulating; it has automatic flow control. When thesource object 901 has filled up the buffer, it hands it back to thetransform 902 through the pushFullBuf function.

The sink 903 is flow controlled as well. It calls nextFullBuf whichtells the transform 902 that it is ready for the next filled buffer.This operation can block the sink 903 until a buffer is ready. When thesink 903 is finished with a buffer (i.e., it has consumed the data inthe buffer) it calls releaseEmptyBuf. ReleaseEmptyBuf gives the bufferback to the transform 902. The transform 902 can then hand that buffer,for example, back to the source object 901 to fill up again. In additionto the automatic flow-control benefit of this method, it also providesfor limiting the amount of memory dedicated to buffers by allowingenforcement of a fixed allocation of buffers by a transform. This is animportant feature in achieving a cost-effective limited DRAMenvironment.

The MediaSwitch class 909 calls the allocEmptyBuf method of theTmkClipCache 912 object and receives a PES buffer from it. It then goesout to the circular buffers in the Media Switch hardware and generatesPES buffers. The MediaSwitch class 909 fills the buffer up and pushes itback to the TmkClipCache 912 object.

The TmkClipCache 912 maintains a cache file 918 on a storage medium. Italso maintains two pointers into this cache: a push pointer 919 thatshows where the next buffer coming from the source 901 is inserted; anda current pointer 920 which points to the current buffer used.

The buffer that is pointed to by the current pointer is handed to theVela decoder class 916. The Vela decoder class 916 talks to the decoder921 in the hardware. The decoder 921 produces a decoded TV signal thatis subsequently encoded into an analog TV signal in NTSC, PAL or otheranalog format. When the Vela decoder class 916 is finished with thebuffer it calls releaseEmptyBuf.

The structure of the classes makes the system easy to test and debug.Each level can be tested separately to make sure it performs in theappropriate manner, and the classes may be gradually aggregated toachieve the desired functionality while retaining the ability toeffectively test each object.

The control object 917 accepts commands from the user and sends eventsinto the pipeline to control what the pipeline is doing. For example, ifthe user has a remote control and is watching TV, the user presses pauseand the control object 917 sends an event to the sink 903, that tells itpause. The sink 903 stops asking for new buffers. The current pointer920 stays where it is at. The sink 903 starts taking buffers out againwhen it receives another event that tells it to play. The system is inperfect synchronization; it starts from the frame that it stopped at.

The remote control may also have a fast forward key. When the fastforward key is pressed, the control object 917 sends an event to thetransform 902, that tells it to move forward two seconds. The transform902 finds that the two second time span requires it to move forwardthree buffers. It then issues a reset event to the downstream pipeline,so that any queued data or state that may be present in the hardwaredecoders is flushed. This is a critical step, since the structure ofMPEG streams requires maintenance of state across multiple frames ofdata, and that state will be rendered invalid by repositioning thepointer. It then moves the current pointer 920 forward three buffers.The next time the sink 903 calls nextFullBuf it gets the new currentbuffer. The same method works for fast reverse in that the transform 902moves the current pointer 920 backwards.

A system clock reference resides in the decoder. The system clockreference is sped up for fast play or slowed down for slow play. Thesink simply asks for full buffers faster or slower, depending on theclock speed.

With respect to FIG. 10, two other objects derived from the TmkXfrmclass are placed in the pipeline for disk access. One is calledTmkClipReader 1003 and the other is called TmkClipWriter 1001. Bufferscome into the TmkClipWriter 1001 and are pushed to a file on a storagemedium 1004. TmkClipReader 1003 asks for buffers which are taken off ofa file on a storage medium 1005. A TmkClipReader 1003 provides only theallocEmptyBuf and pushFullBuf methods, while a TmkClipWriter 1001provides only the nextFullBuf and releaseEmptyBuf methods. ATmkClipReader 1003 therefore performs the same function as the input, or“push” side of a TmkClipCache 1002, while a TmkClipWriter 1001 thereforeperforms the same function as the output, or “pull” side of aTmkClipCache 1002.

Referring to FIG. 11, a preferred embodiment that accomplishes multiplefunctions is shown. A source 1101 has a TV signal input. The sourcesends data to a PushSwitch 1102 which is a transform derived fromTmkXfrm. The PushSwitch 1102 has multiple outputs that can be switchedby the control object 1114. This means that one part of the pipeline canbe stopped and another can be started at the users whim. The user canswitch to different storage devices. The PushSwitch 1102 could output toa TmkClipWriter 1106, which goes onto a storage device 1107 or write tothe cache transform 1103.

An important feature of this apparatus is the ease with which it canselectively capture portions of an incoming signal under the control ofprogram logic. Based on information such as the current time, or perhapsa specific time span, or perhaps via a remote control button press bythe viewer, a TmkClipWriter 1106 may be switched on to record a portionof the signal, and switched off at some later time. This switching istypically caused by sending a “switch” event to the PushSwitch 1102object.

An additional method for triggering selective capture is throughinformation modulated into the VBI or placed into an MPEG private datachannel. Data decoded from the VBI or private data channel is passed tothe program logic. The program logic examines this data to determine ifthe data indicates that capture of the TV signal into which it wasmodulated should begin. Similarly, this information may also indicatewhen recording should end, or another data item may be modulated intothe signal indicating when the capture should end. The starting andending indicators may be explicitly modulated into the signal or otherinformation that is placed into the signal in a standard fashion may beused to encode this information.

With respect to FIG. 12, an example is shown which demonstrates how theprogram logic scans the words contained within the closed caption (CC)fields to determine starting and ending times, using particular words orphrases to trigger the capture. A stream of NTSC or PAL fields 1201 ispresented. CC bytes are extracted from each odd field 1202, and enteredin a circular buffer 1203 for processing by the Word Parser 1204. TheWord Parser 1204 collects characters until it encounters a wordboundary, usually a space, period or other delineating character. Recallfrom above, that the MPEG audio and video segments are collected into aseries of fixed-size PES buffers. A special segment is added to each PESbuffer to hold the words extracted from the CC field 1205. Thus, the CCinformation is preserved in time synchronization with the audio andvideo, and can be correctly presented to the viewer when the stream isdisplayed. This also allows the stored stream to be processed for CCinformation at the leisure of the program logic, which spreads out load,reducing cost and improving efficiency. In such a case, the words storedin the special segment are simply passed to the state table logic 1206.

During stream capture, each word is looked up in a table 1206 whichindicates the action to take on recognizing that word. This action maysimply change the state of the recognizer state machine 1207, or maycause the state machine 1207 to issue an action request, such as “startcapture”, “stop capture”, “phrase seen”, or other similar requests.Indeed, a recognized word or phrase may cause the pipeline to beswitched; for example, to overlay a different audio track if undesirablelanguage is used in the program.

Note that the parsing state table 1206 and recognizer state machine 1207may be modified or changed at any time. For example, a different tableand state machine may be provided for each input channel. Alternatively,these elements may be switched depending on the time of day, or becauseof other events.

Referring to FIG. 11, a PullSwitch is added 1104 which outputs to thesink 1105.

The sink 1105 calls nextFullBuf and releaseEmptyBuf to get or returnbuffers from the PullSwitch 1104. The PullSwitch 1104 can have anynumber of inputs. One input could be an ActionClip 1113. The remotecontrol can switch between input sources. The control object 1114 sendsan event to the PullSwitch 1104, telling it to switch. It will switchfrom the current input source to whatever input source the controlobject selects.

An ActionClip class provides for sequencing a number of different storedsignals in a predictable and controllable manner, possibly with theadded control of viewer selection via a remote control. Thus, it appearsas a derivative of a TmkXfrm object that accepts a “switch” event forswitching to the next stored signal.

This allows the program logic or user to create custom sequences ofvideo output. Any number of video segments can be lined up and combinedas if the program logic or user were using a broadcast studio videomixer. TmkClipReaders 1108, 1109, 1110 are allocated and each is hookedinto the PullSwitch 1104. The PullSwitch 1104 switches between theTmkClipReaders 1108, 1109, 1110 to combine video and audio clips. Flowcontrol is automatic because of the way the pipeline is constructed. ThePush and Pull Switches are the same as video switches in a broadcaststudio.

The derived class and resulting objects described here may be combinedin an arbitrary way to create a number of different usefulconfigurations for storing, retrieving, switching and viewing of TVstreams. For example, if multiple input and output sections areavailable, one input is viewed while another is stored, and apicture-in-picture window generated by the second output is used topreview previously stored streams. Such configurations represent aunique and novel application of software transformations to achieve thefunctionality expected of expensive, sophisticated hardware solutionswithin a single cost-effective device.

With respect to FIG. 13, a high-level system view is shown whichimplements a VCR backup. The Output Module 1303 sends TV signals to theVCR 1307. This allows the user to record TV programs directly on tovideo tape. The invention allows the user to queue up programs from diskto be recorded on to video tape and to schedule the time that theprograms are sent to the VCR 1307. Title pages (EPG data) can be sent tothe VCR 1307 before a program is sent. Longer programs can be scaled tofit onto smaller video tapes by speeding up the play speed or droppingframes.

The VCR 1307 output can also be routed back into the Input Module 1301.In this configuration the VCR acts as a backup system for the MediaSwitch 1302. Any overflow storage or lower priority programming is sentto the VCR 1307 for later retrieval.

The Input Module 1301 can decode and pass to the remainder of the systeminformation encoded on the Vertical Blanking Interval (VBI). The OutputModule 1303 can encode into the output VBI data provided by theremainder of the system. The program logic may arrange to encodeidentifying information of various kinds into the output signal, whichwill be recorded onto tape using the VCR 1307. Playing this tape backinto the input allows the program logic to read back this identifyinginformation, such that the TV signal recorded on the tape is properlyhandled. For example, a particular program may be recorded to tape alongwith information about when it was recorded, the source network, etc.When this program is played back into the Input Module, this informationcan be used to control storage of the signal, presentation to theviewer, etc.

One skilled in the art will readily appreciate that such a mechanism maybe used to introduce various data items to the program logic which arenot properly conceived of as television signals. For instance, softwareupdates or other data may be passed to the system. The program logicreceiving this data from the television stream may impose controls onhow the data is handled, such as requiring certain authenticationsequences and/or decrypting the embedded information according to somepreviously acquired key. Such a method works for normal broadcastsignals as well, leading to an efficient means of providing non-TVcontrol information and data to the program logic.

Additionally, one skilled in the art will readily appreciate thatalthough a VCR is specifically mentioned above, any multimedia recordingdevice (e.g., a Digital Video Disk-Random Access Memory (DVD-RAM)recorder) is easily substituted in its place.

Although the invention is described herein with reference to thepreferred embodiment, one skilled in the art will readily appreciatethat other applications may be substituted for those set forth hereinwithout departing from the spirit and scope of the present invention.For example, the invention can be used in the detection of gamblingcasino crime. The input section of the invention is connected to thecasino's video surveillance system. Recorded video is cached andsimultaneously output to external VCRs. The user can switch to any videofeed and examine (i.e., rewind, play, slow play, fast forward, etc.) aspecific segment of the recorded video while the external VCRs are beingloaded with the real-time input video. Accordingly, the invention shouldonly be limited by the claims included below.

What is claimed is:
 1. A process for the simultaneous storage and play back of multimedia data, comprising the steps of: accepting television (TV) broadcast signals, wherein said TV signals are based on a multitude of standards, including, but not limited to, National Television Standards Committee (NTSC) broadcast, PAL broadcast, satellite transmission, DSS, DBS, or ATSC; tuning said TV signals to a specific program; providing at least one Input Section, wherein said Input Section converts said specific program to an Moving Pictures Experts Group (MPEG) formatted stream for internal transfer and manipulation; providing a Media Switch, wherein said Media Switch parses said MPEG stream, said MPEG stream is separated into its video and audio components; storing said video and audio components on a storage device; providing at least one Output Section, wherein said Output Section extracts said video and audio components from said storage device; wherein said Output Section assembles said video and audio components into an MPEG stream; wherein said Output Section sends said MPEG stream to a decoder; wherein said decoder converts said MPEG stream into TV output signals; wherein said decoder delivers said TV output signals to a TV receiver; and accepting control commands from a user, wherein said control commands are sent through the system and affect the flow of said MPEG stream.
 2. The process of claim 1, wherein said Input Section directs said MPEG stream to the destination indicated by said control commands.
 3. The process of claim 1, wherein said Output Section extracts said video and audio components from the storage device indicated by said control commands.
 4. The process of claim 1, further comprising the step of: creating custom video output sequences, wherein said sequences are specified by a user or program control.
 5. The process of claim 1, wherein the storing and extracting of said video and audio components from said storage device are performed simultaneously.
 6. The process of claim 1, wherein said Media Switch calculates and logically associates a time stamp to said video and audio components.
 7. The process of claim 1, wherein said Media Switch extracts time stamp values from a digital TV stream and logically associates said time stamp values to said video and audio components.
 8. The process of claim 1, further comprising the steps of: placing said video component into a circular video buffer; posting an event in a circular event buffer, wherein said event contains an indication that a video component was found and the location of said video component in said circular video buffer; and sending notice of said event posting.
 9. The process of claim 1, further comprising the steps of: placing said audio component into a circular audio buffer; posting an event in a circular event buffer, wherein said event contains an indication that an audio component was found and the location of said audio component in said circular audio buffer; and sending notice of said event posting.
 10. The process of claims 8 or 9, further comprising the steps of: receiving said notice; retrieving said event posting from said event buffer; and indexing into the appropriate buffer indicated by the type and location information in said event buffer.
 11. The process of claim 10, further comprising the steps of: generating a buffer containing the logical audio or video segments in order, including ancillary information, wherein each of said logical segments points to the appropriate circular buffer location where corresponding audio or video components have been placed.
 12. The process of claim 1, further comprising the step of: increasing the decoder system clock rate for fast playback or fast reverse playback.
 13. The process of claim 1, further comprising the step of: decreasing the decoder system clock rate for slow playback or slow reverse playback.
 14. The process of claim 1, further comprising the step of: combining system audio cues and on-screen displays with said TV output signals.
 15. The process of claim 1, further comprising the steps of: decoding the Vertical Blanking Interval (VBI) data or private data channel information from said TV signal; and examining said data to determine the starting or ending indicators of a specific program.
 16. The process of claim 1, further comprising the step of: scanning the words contained within the closed caption (CC) fields to determine program starting and ending times, wherein particular words or phrases are used to trigger the recording of a specific program and wherein the CC information is preserved in time synchronization with the audio and video, and can be correctly presented to the viewer when the stream is displayed.
 17. The process of claim 16, further comprising the step of: performing a specific action when a specific word is found in said CC information.
 18. The process of claim 1, wherein said Media Switch has a data bus connecting it to a CPU and DRAM.
 19. The process of claim 1, wherein said Media Switch shares an address bus with a CPU and DRAM.
 20. The process of claim 1, wherein said Media Switch operates asychronously and autonomously with a CPU.
 21. The process of claim 1, wherein said storage device is connected to said Media Switch.
 22. The process of claim 1, wherein said Media Switch allows the CPU to queue up Direct Memory Access (DMA) transfers.
 23. The process of claim 1, wherein said Media Switch is implemented in hardware.
 24. The process of claim 1, further comprising the step of: providing a multimedia recording device, including, but not limited to, a Video Cassette Recorder (VCR) or a Digital Video Disk-Random Access Memory (DVD-RAM) device, wherein said recording device is attached to the output side of said decoder, allowing said user to record said TV output signals.
 25. The process of claim 24, wherein said user queues up programs from said storage device to be stored on said recording device.
 26. The process of claim 24, wherein said user sets time schedules for said programs to be sent to said recording device.
 27. The process of claim 24, wherein title pages may be sent to said recording device before sending a program to be stored on said recording device.
 28. The process of claim 24, wherein a program that is longer in duration than a magnetic tape in said recording device allows, is sped up to fit within the desired time limit.
 29. The process of claim 24, wherein a program that is longer in duration than a magnetic tape in said recording device allows, has frames dropped from it to fit within the desired time limit.
 30. The process of claim 24, wherein the output of said recording device is routed to said Input Section, allowing said recording device to act as a storage back up system, said recording device accepts overflow storage, TV programs, software updates, or other data that are later retrieved and sent to said Input Section.
 31. A process for the simultaneous storage and play back of multimedia data, comprising the steps of: providing a physical data source, wherein said physical data source accepts broadcast data from an input device, parses video and audio data from said broadcast data, and temporarily stores said video and audio data; providing a source object, wherein said source object extracts video and audio data from said physical data source; providing a transform object, wherein said transform object stores and retrieves data streams onto a storage device; wherein said source object obtains a buffer from said transform object, said source object converts video data into data streams and fills said buffer with said streams; wherein said source object is automatically flow controlled by said transform object; providing a sink object, wherein said sink object obtains data stream buffers from said transform object and outputs said streams to a video and audio decoder; wherein said decoder converts said streams into display signals and sends said signals to a display; wherein said sink object is automatically flow controlled by said transform object; providing a control object, wherein said control object receives commands from a user, said commands control the flow of the broadcast data through the system; and wherein said control object sends flow command events to said source, transform, and sink objects.
 32. An apparatus for the simultaneous storage and play back of multimedia data, comprising: a module for accepting television (TV) broadcast signals, wherein said TV signals are based on a multitude of standards, including, but not limited to, National Television Standards Committee (NTSC) broadcast, PAL broadcast, satellite transmission, DSS, DBS, or ATSC; a module for tuning said TV signals to a specific program; at least one Input Section, wherein said Input Section converts said specific program to an Moving Pictures Experts Group (MPEG) formatted stream for internal transfer and manipulation; a Media Switch, wherein said Media Switch parses said MPEG stream, said MPEG stream is separated into its video and audio components; a module for storing said video and audio components on a storage device; at least one Output Section, wherein said Output Section extracts said video and audio components from said storage device; wherein said Output Section assembles said video and audio components into an MPEG stream; wherein said Output Section sends said MPEG stream to a decoder; wherein said decoder converts said MPEG stream into TV output signals; wherein said decoder delivers said TV output signals to a TV receiver; and accepting control commands from a user, wherein said control commands are sent through the system and affect the flow of said MPEG stream.
 33. The apparatus of claim 32, wherein said Input Section directs said MPEG stream to the destination indicated by said control commands.
 34. The apparatus of claim 32, wherein said Output Section extracts said video and audio components from the storage device indicated by said control commands.
 35. The apparatus of claim 32, further comprising: a module for creating custom video output sequences, wherein said sequences are specified by a user or program control.
 36. The apparatus of claim 32, wherein the storing and extracting of said video and audio components from said storage device are performed simultaneously.
 37. The apparatus of claim 32, wherein said Media Switch calculates and logically associates a time stamp to said video and audio components.
 38. The apparatus of claim 32, wherein said Media Switch extracts time stamp values from a digital TV stream and logically associates said time stamp values to said video and audio components.
 39. The apparatus of claim 32, further comprising: a module for placing said video component into a circular video buffer; a module for posting an event in a circular event buffer, wherein said event contains an indication that a video component was found and the location of said video component in said circular video buffer; and a module for sending notice of said event posting.
 40. The apparatus of claim 32, further comprising: a module for placing said audio component into a circular audio buffer; a module for posting an event in a circular event buffer, wherein said event contains an indication that an audio component was found and the location of said audio component in said circular audio buffer; and a module for sending notice of said event posting.
 41. The apparatus of claims 39 or 40, further comprising: a module for receiving said notice; a module for retrieving said event posting from said event buffer; and a module for indexing into the appropriate buffer indicated by the type and location information in said event buffer.
 42. The apparatus of claim 41, further comprising: a module for generating a buffer containing the logical audio or video segments in order, including ancillary information, wherein each of said logical segments points to the appropriate circular buffer location where corresponding audio or video components have been placed.
 43. The apparatus of claim 32, further comprising: a module for increasing the decoder system clock rate for fast playback or fast reverse playback.
 44. The apparatus of claim 32, further comprising: a module for decreasing the decoder system clock rate for slow playback or slow reverse playback.
 45. The apparatus of claim 32, further comprising: a module for combining system audio cues and on-screen displays with said TV output signals.
 46. The apparatus of claim 32, further comprising: a module for decoding the Vertical Blanking Interval (VBI) data or private data channel information from said TV signal; and a module for examining said data to determine the starting or ending indicators of a specific program.
 47. The apparatus of claim 32, further comprising: a module for scanning the words contained within the closed caption (CC) fields to determine program starting and ending times, wherein particular words or phrases are used to trigger the recording of a specific program and wherein the CC information is preserved in time synchronization with the audio and video, and can be correctly presented to the viewer when the stream is displayed.
 48. The apparatus of claim 47, further comprising: a module for performing a specific action when a specific word is found in said CC information.
 49. The apparatus of claim 32, wherein said Media Switch has a data bus connecting it to a CPU and DRAM.
 50. The apparatus of claim 32, wherein said Media Switch shares an address bus with a CPU and DRAM.
 51. The apparatus of claim 32, wherein said Media Switch operates asychronously and autonomously with a CPU.
 52. The apparatus of claim 32, wherein said storage device is connected to said Media Switch.
 53. The apparatus of claim 32, wherein said Media Switch allows the CPU to queue up Direct Memory Access (DMA) transfers.
 54. The apparatus of claim 32, further comprising: a multimedia recording device, including, but not limited to, a Video Cassette Recorder (VCR) or a Digital Video Disk-Random Access Memory (DVD-RAM) device, wherein said recording device is attached to the output side of said decoder, allowing said user to record said TV output signals.
 55. The apparatus of claim 54, wherein said user queues up programs from said storage device to be stored on said recording device.
 56. The apparatus of claim 54, wherein said user sets time schedules for said programs to be sent to said recording device.
 57. The apparatus of claim 54, wherein title pages may be sent to said recording device before sending a program to be stored on said recording device.
 58. The apparatus of claim 54, wherein a program that is longer in duration than a magnetic tape in said recording device allows, is sped up to fit within the desired time limit.
 59. The apparatus of claim 54, wherein a program that is longer in duration than a magnetic tape in said recording device allows, has frames dropped from it to fit within the desired time limit.
 60. The apparatus of claim 54, wherein the output of said recording device is routed to said Input Section, allowing said recording device to act as a storage back up system, said recording device accepts overflow storage, TV programs, software updates, or other data that are later retrieved and sent to said Input Section.
 61. An apparatus for the simultaneous storage and play back of multimedia data, comprising: a physical data source, wherein said physical data source accepts broadcast data from an input device, parses video and audio data from said broadcast data, and temporarily stores said video and audio data; a source object, wherein said source object extracts video and audio data from said physical data source; a transform object, wherein said transform object stores and retrieves data streams onto a storage device; wherein said source object obtains a buffer from said transform object, said source object converts video data into data streams and fills said buffer with said streams; wherein said source object is automatically flow controlled by said transform object; a sink object, wherein said sink object obtains data stream buffers from said transform object and outputs said streams to a video and audio decoder; wherein said decoder converts said streams into display signals and sends said signals to a display; wherein said sink object is automatically flow controlled by said transform object; a control object, wherein said control object receives commands from a user, said commands control the flow of the broadcast data through the system; and wherein said control object sends flow command events to said source, transform, and sink objects. 